Current sources based on field effect transistors, MOSFET, or bipolar transistors are used in countless applications for a very wide variety of purposes. The ability of the current source to supply a constant current under different loads, different output voltages and different supply voltages is of great importance in this regard. To achieve this, the current source must be run at the proper operating point under all conditions.
In known implementations of such MOSFET current sources or bipolar current sources, the correct operating point is determined by implementing a regulation of the provided current by monitoring the infed supply voltage, the provided voltage for an electrical load or a drain voltage or collector voltage of the current source, and assessing the operating point on that basis. In the dimensioning of the circuit, a reserve (as defined below) must be planned for in each case in order to indicate incorrect behavior and/or initiate corrective measures that prevent the current source from leaving its operating range. The reserve has the effect, however, that the current source no longer operates in the optimal current range.